Impactful, in our context, means that taking an option during leveling, when finding or selecting an item during a run has a major impact on play. This is in contrast to incremental level options. For example, an impactful level option will double the projectiles from my weapon. An incremental level option might increase my damage 2%. One of the big features of survivors-likes as a genre is highly impactful level options, often to the point of over the top insanity.